Apparatus for mixing a plurality of gaseous streams

ABSTRACT

A method of mixing compressible fluid media (which may include an atomized spray) comprising delivering said media to a mixing zone, at least one said medium being a gas or vapor, and imparting to said gaseous or vaporous medium in the mixing zone a supersonic velocity and/or a sonic vibration, whereby the supersonic velocity and/or the sonic vibration promotes mixing of the fluid media.

llnite States Patent Wiesenberger 1 51 June 6, 197 2 s4] APPARATUS FOR MIXING A 3,064,619 11/1962 Fortman ..239/102 ux PLURALITY OF GASEOUS STREAMS 3,157,359 11/1964 Fortman 239/lO2 3,182,710 5/1965 Mount ..239/102 X [72] Inventor: Josef Wiesenberger, V1enna, Austna 3,240,254 3/1966 Hughes" "239l102 X 73 Assignee; Dumag Ohg, Db Ludwig Kaluza & C0 3,255,998 6/1966 Fiechter.... ..239/102 X wien, Austria 3,297,255 1/1967 Fortman ..239/102 3,326,467 6/1967 Fortman ..239/l02 [22] Filed: Dec. 22, 1969 21 Appl 887 115 Primary Examiner-M. Henson Wood, Jr.

Assistant ExaminerJohn J. Love Att0rneyWoodhams, Blanchard and Flynn [30] Foreign Application Priority Data Apr. 8, 1969 Austria A 3379/69 ABSTRACT A method of mixing compressible fluid media (which may in- U.S. Ci ..239/l02, 239/403 dude an atomized Spray) comprising delivering Said media to [58 1 Field of Search ..239 102, 403, 404, 492 a ""l 9 one med'um 9" and impartlng to sand gaseous or vaporous medlum 1n the mlxing zone a supersonic velocity and/or a sonic vibration, [56] References cued whereby the supersonic velocity and/or the sonic vibration UNITED STATES PATENTS promotes mixing of the fluid media.

1,533,509 4/1925 Morse ..239/492 X 3 Claims, 6 Drawing Figures 1 11 i1 1 1 g 1 e I 3 I l l i '1 1 80 l I G1 [1 1 1 8! I 1 E 1 b 1 I "1' 82 r-s5 g 1 3 I l A 1 llll 1 W 11? i 1 1 PATENTED UH 6 1912 SHEET 2 OF 3 APPARATUS FOR MIXING A PLURALITY F GASEOUS STREAMS The invention relates to a method of and apparatus for mixing compressible fluid media, and particularly for producing combustible mixtures of such fluid media.

The invention has as an object particularly intimate mixturing of particles of two or more compressible fluid media, e.g. to intermix finely dispersed or atomized liquids intimately with a gas, or vapor, and/or to produce an intimate mixture of two or more gases or vapors.

The term compressible fluid medium" is used in this specification and claims to include a gaseousor vapor-borne dispersion of incompressible particles such as droplets of liquid, and includes for example a so-called atomized" spray.

Although the intimate mixing of non-combustible fluid media represents an important application of the invention, its main application lies in the production of combustible mixtures of fluid media, namely atomized combustible liquids or combustible gases with combustion air.

It is to be understood that the terms gas," vapor and liquid" respectively include mixtures of gases, mixtures of vapors and mixtures of liquids.

According to one aspect of the invention, the above object is realized by a method of mixing compressible fluid media as herein defined comprising delivering said media to a mixing zone, at least one said medium being a gas or vapor, and imparting to said gaseous or vaporous medium in the mixing zone a supersonic velocity and/or a sonic vibration, whereby the supersonic velocity and/or the sonic vibration promotes mixing of the fluid media.

Preferably the frequency of the sonic vibration is at least 3,000 Hz.

Another said fluid medium may comprise an atomized spray, said spray having been produced from a liquid by centrifugal force before said another fluid medium is delivered into the mixing zone.

The fluid media may be delivered into the mixing zone via respective concentric nozzles.

In another aspect of the invention, the object is realized by apparatus for mixing compressible fluid media as herein defined, comprising means for delivering said fluid media into a mixing zone, at least one said medium being a gas or a vapor, and means for imparting to said gaseous or vaporous medium in the mixing zone a supersonic velocity and/or a sonic vibration, whereby in operation said supersonic velocity and/or sonic vibration promotes mixing of the fluid media.

The apparatus may comprise a first nozzle adapted to deliver a said fluid medium into the mixing zone, and an annular nozzle concentric therewith, and adapted to deliver said gaseous or vaporous medium to an annular groove adapted to act as a resonator, to impart' said sonic vibration to the gaseous or vaporous medium.

The annular groove may be located opposite the annular nozzle, so that the nozzle discharges gaseous or vaporous medium directly into the annular groove.

Alternatively, there may be a deflecting surface located opposite the annular nozzle and adapted to direct said gaseous or vaporous medium from the annular nozzle to said annular groove.

In another embodiment, the apparatus may comprise a first nozzle adapted to deliver a said fluid medium into the mixing zone, and an annular nozzle concentric therewith, and adapted to deliver said gaseous or vaporous medium into the mixing zone at a supersonic velocity.

The annular nozzle may be a Laval-type nozzle.

The first nozzle may also be an annular noule.

There may be atomizer means for producing an atomized spray from a liquid by centrifugal force, and for delivering said spray through the first nozzle, the first nozzle being the radially innermost of said concentric nozzles.

The atomizer means may comprise a chamber, means for introducing said liquid tangentially into the chamber, and a central outlet which forms said first nozzle.

There may be concentric with the first and annular nozzles a further annular nozzle adapted to deliver a said gaseous or vaporous medium to an annular groove adapted to act as a resonator to impart said sonic vibration to the gaseous or vaporous medium.

The invention will be described, merely by way of example, with reference to the accompanying drawings of which FIGS. 1 to 6 each show an axial cross-section of a different embodiment of the invention. Thus:

FIGS. 1 and 2 each show an apparatus, in which a liquid is atomized and is intimately mixed with a gaseous medium;

FIGS. 3 and 4 each show apparatus in which two gaseous media are intimately mixed;

FIG. 5 shows apparatus in which a liquid is atomized and mixed with a gaseous medium; and

FIG. 6 shows apparatus in which a liquid is atomized and mixed with two different gaseous media, either individually or together.

The apparatus of FIG. 1 has a housing 1, into which is fitted a substantially tubular center part 2, forming a conventional pressure atomizer. Pressurised liquid flows through the center conduit 3, from where it passes through tangential channels 4 into a cylindrical chamber 5, in which the liquid is given a fast rotary movement and from which it issues through the nozzle 7 in atomised fomi as a cone of spray. This central pressure atomizer is combined with a generator of sonic vibrations which consists of the following components.

An inlet conduit 10 with annular cross-section is supplied with pressurized gas, e.g. compressed air. The channel gradually tapers to form an annular nozzle 11 from which the pressurised gas flows at a high velocity directly into an annular groove 12 located on the housing opposite the nozzle outlet. The dimensions of this groove are such that it resonates and sonic vibrations having a frequency of 3,000 Hz or more are imparted to the gas passing through the zone 15 between the annular groove 12 and the surface 14 which defines the front of the center part 2; the spray cone issuing from the nozzle 7 is located within the effective range of these vibrations which persist in the gas as it mixes with the atomized spray. The pressurized gas and the cone of atomized spray intermix in a mixing zone constituted generally by the zone 15 and the zone radially inward thereof and extending axially a short distance from the nozzle 7. The sonic vibrations promote this mixing.

In the embodiment of FIG. 2, the device has also a housing I a pressure atomizer with parts 2 to 7 equivalent to the similarly referenced parts of FIG. 1, located therein. A supply conduit 10 supplies compressed gas to an annular nozzle 11, from which the compressed gas flows via a deflecting surface 13 arranged on the center portion to an annular groove 17 located on the housing which acts as a resonator so that sonic vibrations of a frequency of 3,000 Hz or more are imparted to the gas in the zone 15. A concave surface 18 reflects the sonic vibrations towards, and directs the compressed gas towards, the spray cone issuing from the nozzle 7, so that the compressed gas and the atomized spray mix under the action of the sonic vibrations in a mixing zone constituted generally by the region occupied by the spray cone.

Tests have shown that, contrary to known devices, it is possible in an oil burner similar to the apparatus of FIG. 1 and 2, to reduce the flow rate of atomized liquid to 10 percent of the full load rate without thereby causing any substantial deterioration of the efficiency of combustion. Compared with known mixing apparatus, in which an ultrasonic vibration field is used for the vaporization of a liquid issuing from a nozzle in non-atomized and thus incompressible form, the apparatus shown in FIGS. 1 or 2 has the advantage that the operation of the sonic vibration generator requires only a fraction of the quantity of gas at a substantially lower pressure, so that the operating costs are much lower and the apparatus may also be used economically in installations with comparatively small outputs.

Although a sonic vibration frequency of at least 3,000 Hz has been mentioned, this does not mean that a lower frequency cannot be used. However, below this frequency, the noise generation will be unacceptable for many purposes. Also, the sonic vibrations mentioned throughout this specification and claims may be ultrasonic in the sense that their frequency is above the human audio-frequency range.

The apparatuses shown in FIGS. 3 and 4 are based on the fact that the action of sonic vibrations may also be used for intimately mixing two gases. Tl-Iis applies, for example, to the intensive intermixing of a combustible gas with combustion air.

The mixing nozzle of FIG. 3 has a substantially tubular center portion 21 which contains a supply pipe 22 for a gas, e.g. a combustible gas at a low pressure, such as usually used for town gas, of l to 2.5 atm. Into the front end of the center portion 21 is screwed a conical member 23 which reduces the flow cross-section of the center portion to a narrow annular central nozzle 24 so that the combustible gas flows at an increased velocity, corresponding to the reduction in the crosssection, substantially in the shape of a thin-walled cylinder.

A housing member 26 is screwed onto the center portion 21. A compressed gas, for example, combustion air, is applied to a chamber 27 at a pressure of, say, to 7 atm and flows through axially parallel bores 28 of the center portion into an annular chamber 29 which tapers to form an annular noule 30, by virtue of a conical expansion of the center portion. The housing portion 26 extends beyond the front end of the center part 21 and has, facing the outlet of the annular nozzle 30, an annular groove 31 into which the nozzle 30 directly discharges the compressed gas at high velocity. The groove 31 by virtue of its configuration, acts as a resonator, producing a sonic vibration field of over 3,000 Hz which propagates through gas passing through the chamber 32 and acts thereby on the compressed gas flowing from the annular nozzle 24 to promote the intensive mixing of the two gases in a mixing zone generally beyond the end of the noule 24.

The apparatus of FIG. 4 is of a very similar construction. It has a substantially tubular housing 41 into which leads a supply pipe 42, serving to supply a compressed gas, e.g. combustion air, at a pressure of 5 to 7 Atm. A mushroom-shaped head 43 is fitted into the front end of the center portion 41 so that a shaft 44 of the head 43 forms an annular nozzle 45 with the conically tapering inner wall of the center part 41. The mushroom-shaped head 43 extends beyond the end 41 of the center part and has, facing the annular nozzle 45, an annular groove 46, the dimensions of which are such that it forms a resonator for the compressed gas directed into it at high velocity and under high pressure, and produces a sound vibration of at least 3,000 Hz.

A housing part 47 screwed onto the center part 41 serves here for the separate supply of the second gas, e.g. a combustible gas which is introduced into a chamber 48, flows through the bores 49 and reaches an annular nozzle 50 from which it issues at high velocity in the shape of a substantially hollow cylindrical flow, reaching the zone of the sonic vibration in the gas passing through the chamber 51; the conical end face 52 of the center portion acts as a reflector for the compressed gas and the sonic vibrations directing them towards the flow of the said second gas, whereby mixing takes place generally around the mushroom-shaped head 43.

Instead of being provided with an annular groove 26, acting as a resonator, the mushroom-shaped head 43 may be provided with a deflecting surface which directs the compressed gas towards an annular groove mounted on the center part and acting as a resonator, wherein the function is as described above with reference to FIG. 2.

In the FIG. 3 embodiment, the annular groove 31 may be replaced by a deflecting surface which deflects the flow of compressed gas towards an annular groove provided in the end face of the center portion 21 and acting as a resonator, and in which the sonic vibrations are generated.

In such apparatus as described above for the intensive mixing of gases, and more particularly for producing a combustible mixture of gases, in which a separate noule is provided for each of the gases to be mixed and the gas, the mixing of the gases may be so intensive that, where the gases to be mixed are a combustible gas on the one hand, and air on the other hand, and the mixing ratio is correctly chosen, a complete combustion without any residue can be accomplished with reliability, and with an excellent degree of efficiency.

In another preferred embodiment of the invention, the intimate intermixing of an atomized liquid with a gas is achieved when the spray cone of the atomized liquid is admixed in a mixing zone with a compressed gas issuing at a supersonic velocity from an annular nozzle mounted concentrically to the spray cone. Preferably, the annular nozzle for the compressed gas is a Laval-type nozzle.

The atomized droplets produced by the pressure atomizer pass into the mixing zone occupied by the compressed gas which is flowing at a supersonic velocity and are strongly accelerated. The resulting very large frictional forces, caused by the very large differential speed between droplets and compressed gas, cause the droplets to undergo strong internal vibrations, whereby the cohesion of the droplets is overcome and these droplets disintegrate into a very fine mist.

The compressed gas may be both compressed air or a compressed vapor such as steam, and, where the device is to be used for atomizing combustible liquids for producing a flame, pressurized combustible gas may be used, whereby the calorific energy of the flame produced is further increased.

In this latter case, the following should also be taken into consideration. Due to the high gas velocity, caused by the Lavel-type noule arranged in the burner, a low pressure region is produced inside the center of the spray cone so that hot gases may flow back in the direction of the nozzle, which may have an advantageous effect on the ignition of the fuel mist. The flame is here firmly attached to the burner and detachment of the flame from the burner is less likely.

Apparatuses of this kind are shown in FIGS. 5 and 6. The apparatus of FIG. 5 has a housing 61 into which is screwed a substantially tubular center part 62, into which are fitted two further parts 63 and 64. These parts form together with the center part 62 a conventional pressure atomizer. The pressurized liquid flows in through a center channel 65 and passes through tangential channels 66 into a cylindrical chamber 67 in which the liquid is given a fast rotational movement and from which it issues through the nozzle 68 in the form of an atomized spray cone.

Arranged concentrically surrounding the atomizer 66 to 68, is a supply channel 71 having an annular cross-section formed between the housing parts 61 and 62. The compressed gas is introduced into this channel at 72. The channel 71 tapers to its narrowest point 73 and then expands in the form of a Laval nozzle 74. The dimensions of the Laval nozzle 74 and the pressure of the supplied gas are so selected that the latter leaves the annular Laval nozzle at supersonic velocity. The gas issuing at supersonic velocity acts on the droplets of the spray cone and causes a further breaking up of these droplets into particles forming a very fine mist.

Due to this additional vaporization it is possible to regulate the flow rate of liquid delivered by the pressure vaporizer to about 10 percent of the full load flow rate and to achieve nevertheless the desired complete combustion, owing to the sufiicient vaporization of the liquid fuel, which is not possible when working with a pressure atomizer alone.

It may happen that, owing to scarcity of one liquid fuel, a gaseous fuel must be used, or vice versa, or that only a combustible gas at low pressure is available which, when leaving the Laval nozzle, does not have a supersonic velocity, which thus cannot promote the mixing of the atomized liquid fuel. To provide for these and other cases, where operation must be carried out under widely varying conditions, the apparatus is preferably provided with a further nozzle. Thus, in this preferred embodiment, there may be, concentrically of the central nozzle producing an atomized spray cone, both an an nular nozzle for the delivery of a gas under pressure at supersonic velocity, and a further annular nozzle for delivering a compressed gas, with an associated resonator for imparting a sonic vibration thereto.

FIG. 6 shows a device of this kind in axial longitudinal section, This device comprises in its center portion the entire device shown in FIG. 5, that is to say, an atomizer 66, 68, 67, which receives pressurized liquid through a center conduit 65 and a concentrically mounted annular noule 73, 74 which is supplied with compressed gas through a conduit 72 with annular cross-section.

The housing part 61 has, in this device, a further housing part 80 screwed thereto so as to form a further annular conduit 81 which is adapted to receive a gaseous pressure medium through conduits 82 provided in the housing part 62. The annular conduit 81 terminates at its front end in an annular nozzle 84 directed towards radially inwardly the center, and opposite which is an annular groove 85, open towards the nozzle 84 so as to directly receive gas therefrom and arranged at the front end of the housing part 61. The groove 85 acts as a resonator for the compressed gas issuing from the nozzle 84 and imparts thereto sonic vibrations which persist in the gas as it mixes with the medium issuing from the nozzle 68 or from the nozzle 74 and acting so as to promote the mixing thereof.

Such a multiple nozzle may be operated in many ways so that, for example, in the case of a burner nozzle for operating an industrial furnace, the following possibilities offer themselves:

Operation with fuel oil (nozzle 68) and fuel gases (nozzle 74);

Operation with fuel oil (nozzle 68), fuel gas (nozzle 74) and compressed air or live steam (nozzle 84);

. Operation with fuel oil (nozzle 68) and compressed air or live steam (nozzle 84);

. Operation with fuel gas (nozzle 74) and compressed air or live steam (nozzle 84);

. Operation with fuel gas (nozzle 74) and compressed fuel gas (nozzle 84);

Operation with fuel oil (nozzle 68) and compressed air or live steam (nozzle 74) and compressed fuel gas (nozzle 84). In this case, it will be appreciated that mixing is promoted both by sonic vibrations in the fiiel gas, and the supersonic velocity of the air or live steam.

I claim: 1. An apparatus for mixing a plurality of gaseous streams, comprising:

housing means;

first and second independent nozzle means on said housing means concentrically disposed with respect to each other;

means defining a first passageway in said housing means for supplying a first gaseous stream to said first nozzle means, said first nozzle means including a first annular nozzle and sonic generator means located in the path of flow of said first gaseous stream from said first annular nozzle, said sonic generator means imparting a sonic vibration to said first gaseous stream as same flows therepast;

means for supplying said first gaseous stream from said sonic generator means to a mixing zone adjacent the downstream end of said first and second nozzle means;

means defining a second passageway in said housing means separate from said first passageway means for supplying a liquid to said second nozzle means, said second nozzle means including a second noule encircled by said first annular nozzle and including liquid atomizing chamber means having means defining an outlet opening therefrom to reduce said liquid to fine particles or a second gaseous stream;

means for supplying said second gaseous stream from said liquid atomizing chamber means to said mixing zone; and

third nozzle means separate from said first and second nozzle means and located between said first and second nozzle means and means definin a third passageway separate from said first and secon passageway means for supplying a third gaseous stream thereto, said third nozzle means including a third annular nozzle and means for increasing the velocity of said third gaseous stream to a supersonic level from said third annular nozzle into said mixing zone.

2. An apparatus according to claim 1, wherein said sonic generator means includes an annular grove located in the path of flow of said first gaseous stream from said first annular nozzle, said annular groove being resonant to the flow of said first gaseous stream therethrough to impart a sonic vibration to said first gaseous stream.

3. An apparatus according to claim 2, wherein said first annular nozzle means includes gaseous stream guide means for deflecting said first gaseous stream into said annular groove. 

1. An apparatus for mixing a plurality of gaseous streams, comprising: housing means; first and second independent nozzle means on said housing means concentrically disposed with respect to each other; means defining a first passageway in said housing means for supplying a first gaseous stream to said first nozzle means, said first nozzle means including a first annular nozzle and sonic generator means located in the path of flow of said first gaseous stream from said first annular nozzle, said sonic generator means imparting a sonic vibration to said first gaseous stream as same flows therepast; means for supplying said first gaseous stream from said sonic generator means to a mixing zone adjacent the downstream end of said first and second nozzle means; means defining a second passageway in said housing means separate from said first passageway means for supplying a liquid to said second nozzle means, said second nozzle means including a second nozzle encircled by said first annular nozzle and including liquid atomizing chamber means having means defining an outlet opening therefrom to reduce said liquid to fine particles or a second gaseous stream; means for supplying said second gaseous stream from said liquid atomizing chamber means to said mixing zone; and third nozzle means separate from said first and second nozzle means and located between said first and second nozzle means and means defining a third passageway separate from said first and second passageway means for supplying a third gaseous stream thereto, said third nozzle means including a third annular nozzle and means for increasing the velocity of said third gaseous stream to a supersonic level from said third annular nozzle into said mixing zone.
 2. An apparatus according to claim 1, wherein said sonic generator means includes an annular grove located in the path of flow of said first gaseous stream from said first annular nozzle, said annular groove being resonant to the flow of said first gaseous stream therethrough to impart a sonic vibration to said first gaseous stream.
 3. An apparatus according to claim 2, wherein said first annular nozzle means includes gaseous stream guide means for deflecting said first gaseous stream into said annular groove. 